In many fields and for various reasons, there is often a need to provide sealing, e.g. by closing off an opening in tubing, and this applies regardless of whether the opening is provided deliberately or by accident. However, in some cases it is not always easy to gain access to the outside of the opening through the tubing in order to press any kind of closure pad thereover.
Techniques have therefore been developed to provide sealing or closure from the inside of the tubing. A pad is inserted into the tubing having an opening and is then pressed against the opening from the inside. In order to obtain good sealing when pressing a pad over an opening, various factors need to be taken into consideration, for example the nature of the materials used, i.e. the tubing material and the pad material. An important one of such factors is the force or pressure applied to the pad, and in particular the effective force or pressure around the edges or margin of the opening.
When a pad is applied to the outside of tubing, it is generally fairly easy to ensure that a desired amount of force is used and in particular to find an easily accessible bearing point or surface from which to apply the force. In contrast, when closing an opening from inside the tubing, finding a suitable bearing point is more difficult, particularly when the tubing is to continue to convey a flow of fluid (gas or liquid).
Special closure structures have already been made to solve this problem. These structures comprise a central core constituted by a rigid cylindrical sleeve forming a portion of continuous ducting, with the outside diameter of said portion of ducting being less than the inside diameter of the tubing to be sealed. A flexible resilient membrane is placed around the sleeve and is fixed in sealed manner at each of its ends to the ends of the sleeve so as to form an deformable sealed annular chamber around the sleeve. A small pipe is provided for admitting a fluid, e.g. a gas, under pressure into said annular chamber, thereby allowing it to be inflated at will.
In order to seal an opening in tubing, this structure is inserted inside the tubing and the free end of the small pipe is kept accessible from the outside. When the membrane is properly located facing the opening, fluid is injected at a predetermined pressure via the small pipe. The annular chamber is thus inflated, and as it inflates a portion of its outside surface is pressed closely against the entire inside surface of the tubing, including the opening and the wall around the opening.
The opening is closed by pressing a pad constituted by the portion of the membrane which presses against the rim of the opening, with the force applied being determined by the pressure inside the annular chamber and with the bearing surface providing a reaction to said force being constituted by the surface of the tubing which comes into contact with the membrane forming the outside wall of the annular chamber. The rigid cylindrical sleeve is thus located substantially in the middle of the tubing, thereby ensuring continuity for fluid flow.
This technique gives very good results in any tubing having a wall which is capable of withstanding pressure over its entire surface area.
However, there exist various kinds of tubing whose walls cannot withstand pressure over their entire surface area. This applies, for example, in medical applications concerning the trachea (i.e. the windpipe).
The trachea is generally tubular, but is definitely not a circular cylinder, and it is made up of two portions. The first portion is gutter-shaped, having a generally U-shaped cross section, and it is relatively rigid by virtue of reinforcing cartilage. The second portion interconnects the two longitudinally-extending edges of the gutter. This second portion is fibrous, and very flexible to the point of being fragile.
Thus, when applying forced ventilation to a patient via the trachea, it is highly dangerous to provide peripheral sealing by means of a structure of the type described above because of the fragile second portion of the trachea.
Preferred implementations of the present invention provide a device for sealing tubing while avoiding the above drawback, said device being particularly applicable to closing an opening through the wall of tubing and to providing peripheral sealing around the opening when the tubing in question is a trachea.